 ;; *** Axis grid definition (:grid)
 ;;
 ;; *Note:* If no `:grid` spec is given in the main spec, no background
-;; *grid will be displayed...
+;; *grid will be displayed. If the axis is not `:visible`, the grid
+;; *will still be displayed as long as either `:major` or `:minor`
+;; *ticks are defined in the axis spec.
 ;;
 ;; | *Key*      | *Value* | *Required* | *Default*       | *Description*                                            |
 ;; |------------+---------+------------+-----------------+----------------------------------------------------------|

        great?  (> (m/abs-diff x1 x2) m/PI)]
    (svg/group
     (merge {:stroke "#ccc" :stroke-dasharray "1 1"} attribs)
     (if (:visible x-axis)
       (map
        #(let [x (scale-x %)] (svg/line (project [x y1]) (project [x y2])))
        (select-ticks x-axis minor-x)))
     (if (:visible y-axis)
       (map
        #(let [y (scale-y %)]
           (if circle

;; | `:range`       | vec of range bounds  | Y          | nil                                    | Lower & upper bound of projected coordinates                             |
;; | `:pos`         | number               | Y          | nil                                    | Draw position of the axis (ypos for X-axis, xpos for Y-axis)             |
;; | `:major`       | seq of domain values | N          | nil                                    | Seq of domain positions at which to draw labeled tick marks              |
;; | `:minor`       | seq of domain values | N          | nil                                    | Seq of domain positions at which to draw minor tick marks                |
;; | `:major-size`  | number               | N          | 10                                     | Length of major tick marks                                               |
;; | `:minor-size`  | number               | N          | 5                                      | Length of minor tick marks                                               |
;; | `:label`       | function             | N          | =(default-svg-label (value-format 2))= | Function to format & emit tick labels                                    |
